Allergy is a hypersensitivity disorder of the immune system. In simple terms, Allergy is an over- reaction by our body to some or many common things including food. Allergic reactions occur to normally harmless environmental substances known as allergens. Common allergic reactions include eczema, hives, hay fever, asthma attacks, food allergies, and reactions to the venom of stinging insects. When an allergen comes in contact with the body, it causes the immune system to develop an allergic reaction in persons who are allergic to it. When you inappropriately react to allergens that are normally harmless to other people, you are having an allergic reaction and can be referred to as allergic or atopic. Therefore, people who are prone to allergies are said to be allergic or "atopic."
Dust allergy is the most common allergy in India, triggering reaction in four of five of 5,400 people tested for allergies from across the country. Data of allergy tests at Dr Lal PathLabs shows that 80.3 % people tested were allergic to dust mites. Allergy triggers in India are quite different from the West. “While dust mites cause 80 % of all allergies in India, dust is the second common allergen in the US and Europe, where pollen allergy accounts for 20 % of allergies,” says Dr Arvind Lal, CMD, Dr Lal PathLabs, which collected samples from its 650 collection centres across India.
Dust mites are present in air, fabric, pillows and bedding materials in plenty. They live on materials shed from human body. Many are allergic to the excreta of these mites. In warm and humid climates female mite lays 40-to 80 eggs. More than 10 micro grams per gram of dust is a risk factor for acute Asthma. So it is important to know whether one is allergic to Dust mite or not. If someone is found to be allergic, now oral de-sensitizing vaccine is available. Thanks to the modern DNA recombinant technology!
In our centre, the commonest insect allergen diagnosed is Cockroach
Cockroaches are one of the most common and allergenic of indoor pests. Recent studies have found a strong association between the presence of cockroaches and increases in the severity of asthma symptoms in individuals who are sensitive to cockroach allergens.
These pests are common even in the cleanest of crowded urban areas and older dwellings. They are found in all types of neighborhoods. The proteins found in cockroach saliva are particularly allergenic but the cockroach allergen also comes from dead roaches and roach droppings. It collects in house dust and may persist in the home for some months even after the cockroaches are eradicated.
It is thought that the reason some people are supposedly allergic to chocolate is by virtue of included cockroach protein. Apparently, when the dried cacao beans are gathered up, they are typically covered in cockroaches and some beasties and droppings come along for the ride.
When a Kitten or Puppy is brought to a family, why after some months only some of the members develop allergies like sneezing, asthma, conjunctivitis, itching etc?
The job of our immune system is to neutralize or eliminate foreign substances entering or coming in contact with our body. One of the ways it does this is to create protective proteins called antibodies that are specifically targeted against particular foreign substances. These antibodies, or immunoglobulins (IgG, IgM, IgA, IgD and IgE), are protective and help destroy a foreign particle by attaching to its surface, thereby making it easier for other immune cells to destroy it.
IGE is an antibody that all of us have in small amounts. Allergic persons, however, produce IgE in large quantities. Normally, this antibody is important in protecting us from parasites, but not from cat or dog dander or other allergens. During the sensitization period, cat dander IgE is being overproduced and coats certain potentially explosive cells that contain chemicals. These cells are capable of causing an allergic reaction on subsequent exposures to the dander. This is because the reaction of the cat dander with the dander IgE irritates the cells and leads to the release of various chemicals, including histamine. These chemicals, in turn, cause inflammation and the typical allergic symptoms. This is how the immune system becomes exaggerated and primed to cause an allergic reaction when stimulated by an allergen.
That is why, on exposure to cat or dog, only some members developed allergic symptoms.
Mild allergies like hay fever are highly prevalent in the human population and cause symptoms such as allergic conjunctivitis, itchiness, and runny nose. Allergies can play a major role in predisposing asthma in many individuals. In some people, severe allergies to environmental or dietary allergens or to medication may result in life-threatening anaphylactic reactions.
Many allergens such as dust or pollen are airborne particles. In these cases, symptoms arise in areas in contact with air, such as eyes, nose and lungs. For instance, allergic rhinitis, also known as hay fever, causes irritation of the nose, sneezing, and itching and redness of the eyes. Inhaled allergens can also lead to asthmatic symptoms, caused by narrowing of the airways (bronchoconstriction) and increased production of mucus in the lungs, shortness of breath (dyspnea), coughing and wheezing.
Although fewer humans are allergic to dogs than to cats (link to cat article), canines dander (dead skin cells), saliva, and urine can cause allergic reactions in as much as 10 percent of the population. The hair of furry animals like dogs also can pick up dust, pollen, and other allergens that set off reactions in people (but the hair itself is not an allergen). Pet dander can travel on clothing or reside in carpeting.
For people without allergies, a dog bounding up to them and licking their face can be a happy occasion. Its an altogether different feeling when this happens to a person who is allergic to dogs. For these individuals, the animals allergens land on facial membranes and cause eyes to itch, tear, and burn and the nose to get stuffy.And, for people with asthma, pet dander is a common trigger that can cause symptoms to flare up or worsen.An allergy sufferer scratched by a dog can find the impacted area turning red and becoming highly irritated.
When there are low levels of allergens or low sensitivity to them, dog allergy symptoms may take time to manifest. In some people, symptoms can be more severe and appear quickly, such as when airborne particles get into the lungs, are inhaled, and mix with antibodies. Highly sensitive people can experience severe breathing problems within 15 minutes to 30 minutes and even get a rash on the upper chest, neck, and face.
Mouse urine and faeces could be an important cause of childhood asthma in inner cities
"Although cockroach allergen is the most important factor in terms of asthma severity, we have found that mouse allergen is much more important than dust mite s or allergies to cats or dogs," says Robert Wood of Johns Hopkins University in Baltimore.
The team took samples from the homes of over 600 asthmatic children in eight US cities. Traces of mouse urine or faeces were found in at least one room in 95 per cent of the homes. Tests showed nearly one in five of the children were allergic to the mouse traces and these children tended to have more severe asthma.
Mouse eradication programmes should be carried out: "Most of our asthma patients lived in flats. Even if you keep your own area clean, mice will still get in from other homes."